Update scripts/ecosystem_all_check.sh (#5737)

## Summary

These changes make `scripts/ecosystem_all_check.sh --select ALL` work
again, i forgot to update this script to the new directory structure
from #5299 because it's only run manually


## Test Plan

n/a

scripts/ecosystem_all_check.py

@@ -50,7 +50,7 @@ def main() -> None:
     successes = 0
     errors = 0
     for repository in tqdm(repositories):
-        project_dir = checkouts.joinpath(repository.org).joinpath(repository.repo)
+        project_dir = checkouts.joinpath(f"{repository.org}:{repository.repo}")
         if not project_dir.is_dir():
             tqdm.write(f"Missing {project_dir}")
             errors += 1

scripts/ecosystem_all_check.sh

@@ -7,6 +7,7 @@
 #
 # Usage:
 # ```
+# cargo build --release --target x86_64-unknown-linux-musl --bin ruff
 # scripts/ecosystem_all_check.sh check --select RUF200
 # ```